The invention relates to a bone plate assembly for the immobilization of bones or bone fragments. Particularly, the invention relates to a bone plate assembly comprising a bone plate and a bone anchor, the bone plate assembly allowing an enlarged angle of inclination to one side for the bone anchor with respect to a vertical axis through the plate at a position of a bone anchor hole.
US 2012/0059425 A describes a bone plate assembly with a polyaxial coupling between the bone anchors of the bone plate assembly and the plate member with an increased range of angular motion and a low profile.
Lorich D G and Gardner M J describe a limited-contact dynamic compression plate assembly with elongated holes allowing 25° inclination of a bone anchor in the longitudinal plane, and up to 7° inclination in the transversal plane (Ruedi T P, Buckley R, Moran C G (2007) AO Principles of Fracture Management. 2nd ed. Vol. 1. Stuttgart New York: Thieme-Verlag).
In the field of spinal surgery, U.S. Pat. No. 8,409,260 B2 describes a bone fixation assembly with a bone anchor and a receiving part allowing an enlarged pivot angle of the bone anchor to one side.
While the known bone plate assemblies can provide polyaxial adjustment of the bone screws relative to the bone plate with an equal angle of inclination to each side, there is still a need for an improved bone plate assembly which allows for an increased angle of inclination with respect to a vertical axis through the plate at a position of a bone anchor hole to a favored side, while still providing a low profile of the plate-screw construct as well as high stability. For example, there might be anatomical situations where the angle of inclination relative to a vertical axis through the plate at a position of a bone anchor hole should be increased to only one side. This may be the case, for example, in the context of fractures of the hand or the shoulder.